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Why has H4 Use not effect ? Please need explanation !

 
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Andreas



Joined: 25 Oct 2004
Posts: 136

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Why has H4 Use not effect ? Please need explanation !
PostPosted: Sat Jan 27, 2007 5:32 am     Reply with quote
Hi Friends !

I'am working now since 2 years with the CCS Compiler and discovered now a very odd problem:

Code:

#include <18F8720.h>

#device ICD=TRUE
#device adc=8
#device *=16

#use delay(clock=  8000000)
//#use delay(clock=  32000000)

#fuses NOWDT,WDT128,H4, NOPROTECT, NOOSCSEN, BROWNOUT, BORV25, PUT, NOCPD, STVREN, DEBUG, NOLVP, NOWRT, NOWRTD, NOWAIT, MCU, NOWRTC, NOWRTB, NOEBTR, NOEBTRB, NOCPB

#use rs232(baud=38400,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,stream=com1,errors)

#define TEST PIN_A3

#include <stdio.h>


//--------------------------------
#int_timer3
void timer3_isr()
{
set_timer3(0xF830);
//output_toggle(test);
}

//--------------------------------
void main()
{
   setup_wdt(WDT_OFF);
   setup_timer_0(RTCC_INTERNAL);
   setup_timer_2(T2_DIV_BY_16,0xFF,8);
   setup_timer_3(T3_INTERNAL|T3_DIV_BY_1);
   setup_vref(FALSE);
   set_timer3(0xF830);         // Setup Timer3 as ms Timer @ 32 MHz


fprintf(com1,"Test Message at COM1 @38400 Bd ???\n\r");
enable_interrupts(int_timer3);
enable_interrupts(global);

//--------------------------------
while(1)                         // MAIN LOOP Starts Here
{
output_toggle(test);
delay_ms(1);
output_toggle(test);

} //while(1)
} //main


This code works fine, execpt I am expecting the CPU to run at 32MHz with a 8MHz Quarz !!!!

But as You can see the delay directive says 8MHz !! The baudrate and the delay is working correct with this settings.

Where to I miss the point for using the x4 PLL ????

Anybody out there has an idea ??

best regards and greetings from vienna

Andreas
 
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Sat Jan 27, 2007 7:07 am     Reply with quote
You must specify 32000000 in the use delay. Also, the first time you set the H4 fuse, you must power off the board and then back on. Search the forum and you will find many examples of the same problem.
Andreas



Joined: 25 Oct 2004
Posts: 136

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PostPosted: Sat Jan 27, 2007 12:20 pm     Reply with quote
Hello Mark !

Thanks a lot for Your fast reply !

Of course this was the problem, now looking in the past I could remember that I had sometimes this behaviour and it was gone somewhere, because I must have powered down the device at night time !!!

I am now trying to find a note at the microchip decsheets

Thanks and best regards
Andreas
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